hypothetically? it could get confusing. any hosts with schizophrenia that mainfests voices or hallucinations needs to be very careful with making tulpas, it can go badly.
apart from it just crowding up the limited headspace, it should be easy enough to achieve, but whether its safe is a whole other matter

I have Schizophrenia and I have a Tulpa that I can audibly hear. having Schiz and Tulpamancy isn't as dangerous as many people like to suggest. As long as you know what to do. If after making a Tulpa it acts in a manner that causes suffering talk with the tulpa... Teach it the importance of Morals.. If you have a higher power pray for it to guide your Tulpa to be more manageable the best thing is to teach it the importance of Morals. If after months of trying to guide your tulpa and it still is unmanageable. Visualize your tulpa in your wonderland and speak to it. Ask it what it wants, what it needs.. What will make it happy? Then once you know what it wants, needs, what will make it happy.. Set yourself up for a meditation practice twice a day for 30 minutes. First, start off with relaxation... Just sit and relax your body and watch your breath and meditate. Once relaxed visualize your body turning into an endless supply of the feelings it desires.. Your body is an endless supply of nectar of the feeling the Tulpa needs. Let the Tulpa feed on the nectar. Do this practice until the Tulpa is satisfied. His/Her attitude will change.

Also when talking to your Tulpa you should have an optimistic attitude.. Thinking negatively will only build up more negativity. Think that your Tulpa will recover and keep an optimistic attitude. Tulpas cannot make you do things you don't want them to.. It is a new voice within the system of your mind. If you have schizophrenia you probably already deal with voices.. A Tulpa is a new voice that can be guided to be a positive voice within your system. Try to guide them to be your best friend. Feed them love and caring.

As a last resort. If after many months of trying and your tulpa is still malicious. You have the option to use deconstruction techniques.. One way is to visualize your tulpa in front of you.. Picture it's entire body in front of you and hold it for a short while.. Visualize you Tulpa slowly disappearing.. until it's gone. Repeat doing this for 20 minutes twice a day. Visualize then dissipate.. visualize then dissipate.. This is considered a more compassionate technique. I've found that this other technique can be more effective but less compassionate. Visualize your tulpa in front of you hold it for a short while then engulf it into flames until it is completely devoured. Then send the ashes to the sun and let the sun eradicate whats left so there is no trace of the tulpa left.. Visualize then burn then visualize then burn and do this for 20 minutes twice a day.

This is th ebest advice I can give to a person with Schiz who is interested in Tulpamancy. If you have any questions ask away.. Good luck

Don't believe the things I say just because I tell you.. Test these things and prove them to yourselves so that you know them to be true. ~The Buddha